28-year-old obese man had microscopic hematuria. Physical examination results were normal. His medical history was unremarkable, and there was no pertinent family history. Excretory urography (Fig 1) and computed tomography (CT) of the abdomen (Fig 2) were performed after oral and intravenous administration of contrast material.

Imaging Findings

The excretory urogram demonstrated bilateral nephromegaly with distortion of the pelvocaliceal systems (Fig 1). The CT scan of the abdomen (Fig 2) showed fluid collections in the perinephric space bilaterally, surrounding the renal cortex. In addition, there were peripelvic fluid collections bilaterally, with distortion of the pelvocaliceal systems. There were fluid collections in the retroperitoneum that crossed the midline at the level of the renal hila, adjacent to the abdominal aorta and the inferior vena cava.

Discussion

Several differential diagnostic possibilities are to be considered with bilateral nephromegaly with pelvocaliceal splaying and distortion. Adult polycystic kidney disease, lymphoma, nephroblastomatosis, and other causes of multiple renal masses, such as von Hippel-Lindau disease and tuberous sclerosis, are considerations. Adult polycystic kidney disease has characteristic findings of numerous bilateral renal cysts, with or without hepatic or pancreatic cysts. The cysts typically vary in size and are scattered throughout the parenchyma. Lymphoma and other malignancies can demonstrate soft-tissue masses involving the kidneys, pelvocaliceal systems, or retroperitoneum. The fluid attenuation of the perinephric collections in the test case, as evidenced by attenuation measurements of 0–10 HU in Figure 2c, exclude lymphoma and other soft-tissue masses. Perinephric and retroperitoneal soft-tissue masses can be seen in retroperitoneal fibrosis but are again excluded by the fluid attenuation in the test case. Nephroblastomatosis is a cause of nephromegaly in children and is characterized by multiple subcapsular and parenchymal soft-tissue nodules composed of metanephric blastema (1).

Renal lymphangiectasia is a rare disorder. Patient symptoms described in the literature (2–4) include hematuria, flank pain, and abdominal pain. The condition has been found in children and in adults (2,4–7). The origin of this disorder is speculative. There is a familial association in some cases, which argues for a congenital cause (6). There was no known family history of renal lymphangiectasia in the test case. Others argue for an acquired cause, which suggests that the lymphatic vessels may become blocked owing to inflammation or other obstruction and so cause lymphatic ectasia (8). Others have suggested that these lesions may be a true neoplasm (9). The nomenclature of this disorder is confusing and has evolved in recent years. Other names have included "renal lymphangiomatosis" (3,6), "renal lymphangioma" (5), "peripelvic lymphangiectasia" (2), and "renal peripelvic multicystic lymphangiectasia" (8). "Renal lymphangiectasia" is the preferred name, given that the disorder is characterized by ectatic perirenal, peripelvic, and intrarenal lymphatic vessels (10,11).

Imaging findings of renal lymphangiectasia include peripelvic cysts and perirenal fluid collections. The finding of retroperitoneal fluid collections, presumably dilated lymphatic vessels, is a more variable finding but has been noted in multiple cases in the literature (2–4,6).

Renal lymphangiectasia has been found associated with renal venous thrombosis and hypertension (4,6,12). Ascites and large perinephric fluid collections have been found and are exacerbated by pregnancy (6). The natural history of this disorder is not completely understood.

In a neonatal case, partial regression was reported (7).

The diagnosis of renal lymphangiectasia can be confirmed with needle aspiration of chylous fluid from the perinephric fluid collections (4). However, the ultrasonographic and CT findings are characteristic for this disease and allow the diagnosis to be made confidently (2,6). Treatment is not usually necessary. Complicated cases may be treated with nephrectomy, percutaneous drainage, or marsupialization (4).

In the case presented here, the diagnosis of renal lymphangiectasia was based on the characteristic CT findings. The perirenal, peripelvic, and retroperitoneal collections had attenuation measurements consistent with fluid (0–10 HU) rather than with the soft-tissue attenuation seen with lymphoma or other causes of bilateral renal soft-tissue masses (Fig 2c). No invasive procedures to confirm diagnosis were deemed appropriate for this patient.

Our congratulations to the 26 individuals who submitted the most likely diagnosis (renal lymphangiectasia) for Diagnosis Please, Case 34. The names and locations of the individuals, as submitted, are as follows

Support group for parents, patients, children who suffer from all forms of lymphangiectasia. This condition is caused by dilation of the lymphatics. It can affect the intestinal tract, lungs and other critical body areas.